The checksum isn’t correct in that address. The correct checksum is "0x964d9D1A532B5a5DaeacBAc71d46320DE313AE9C".

When using Etherscan, if the checksum is wrong, it lowercases the address and computes the address itself. If you notice on the Etherscan page it has corrected the checksum for you too. :)

There is a standard for checksummed addresses that also includes the chain ID:

https://eips.ethereum.org/EIPS/eip-1191

Basically, the chain ID is prepended to the address hex, e.g. toChecksum, which produces different checksums for different chains to help prevent mistakes in cross-chain transfers.

After a quick brute-force check, I discovered that the address 0xd93a53B5F382F2a51A4AE3879ABC8F789Bd60e6b is checksummed for chain ID 57245, but you are trying to submit this to the Mainnet with chain ID 1, which is causing the failure. To work around this, you can a) lowercase the address before checking the balance, b) ensure it is checksummed for the correct chain ID, or c) use the older checksum format that does not include the chain ID.

The simple answer is that in solidity:

address(0xa54D3c09E34aC96807c1CC397404bF2B98DC4eFb);

It is true that the compiler warns you of incorrect checksum when it sees one, but that warning is probably there just to tell you that you might have gotten the wrong address altogether (because typically, constant addresses are copy-pasted from one place to another, and copy-pasting would not "accidentally" change some upper-case letter to lower-case or vice versa).

The Solidity compiler tells you exactly how you can fix it (manually):

SyntaxError: This looks like an address but has an invalid checksum. Correct checksummed address: "0xa54d3c09E34aC96807c1CC397404bF2B98DC4eFb". If this is not used as an address, please prepend '00'. For more information please see solidity.readthedocs.io/en/develop/types.html#address-literals address(0xa54D3c09E34aC96807c1CC397404bF2B98DC4eFb);

The solution then becomes:

Hexadecimal literals that pass the address checksum test, for example 0xdCad3a6d3569DF655070DEd06cb7A1b2Ccd1D3AF are of address payable type. Hexadecimal literals that are between 39 and 41 digits long and do not pass the checksum test produce an error. You can prepend (for integer types) or append (for bytesNN types) zeros to remove the error.

But again, these two constants are identical, and they will yield the exact same runtime-behavior.

I created this simple tool that you can use to convert a list of non-checksummed addresses to checksummed addresses.

You can preview it and use it here: https://raw.githack.com/jeremythen/emv-checksum-address-convertor/main/index.html

This is the GitHub repo: https://github.com/jeremythen/emv-checksum-address-convertor

Check the README.md file to learn how to use it. But I think it's straightforward. Simply paste the list of non-checksummed addresses and hit the Convert button. If your list of addresses has the format [0xa1..., 0xa2...], then check the Addresses in array? checkbox so it parses it and returns the result in the same format, ready to copy and paste.

Remember the chain Id. If it's Ethereum, then leave it empty. If it's any other chain, then check the correct chain Id to use here: https://chainlist.org/

You can also use the backend tool in the index.js file, to use it with nodejs or something like that.

I hope it helps.

Check the screenshots below for an example:

Here is how the address with the valid checksum should look like: 0xCf5609B003B2776699eEA1233F7C82D5695cC9AA (note the different case of letters).

Here is the specification of the checksum: https://github.com/ethereum/EIPs/blob/master/EIPS/eip-55.md

To fix the checksum use this method web3.utils.toChecksumAddress().

Alternatively put your address to the url for etherscan like this https://etherscan.io/address/0xCF5609B003B2776699EEA1233F7C82D5695CC9AA then copy the address with valid checksum on the loaded page.